module chapter2;
#include <cmath>

namespace section6{
    int turnNum(int a/*必须是三位数*/){
        if (a/1000>=1||a/1000>0.1){
            return a;
        }
        int x=a/100;
        int y=(a/10)%10;
        int z=a%10;
        int ans=z*100+y*10+x;
        return ans;
    }

    float HelenFormula(float a,float b, float c){
        float p=(a+b+c)/2;
        float ans= sqrt(p*(p-a)*(p-b)*(p-c));
        return ans;
    }
}
